At 60% health, he transitions to Phase 2, wherein he retreats to his Assault Cannon in the front of the car, and the sides of the train car open up allowing access to the middle and front portions of the encounter area.

One of the time consuming portions of Phase 2 involves killing adds, looting them and using Homing Shell on the Assault Cannon. Each shell does 25% of the cannon's health, so 4 shells alone are required to break Nitrogg out (or 3 shells and another 25% of direct damage to the cannon).

It's possible to annihilate the Assault Cannon with a SINGLE Homing Shell thus shortening this encounter SIGNIFICANTLY. To do so, you need 1 Shaman, or 2 Hunters (a single Hunter works, it is just less effective and won't shorten the fight by as much).

The more people that stand in the fire, the faster the stacks will appear on the cannon.

Note that all the while all of this is happening, more adds will be spawning and should be picked by the tank.

Once the Assault Cannon has 9 stacks of Slag Blast, everyone should move out of the fire, and the DPS in the Blackrock Turret should use Homing Shell on it. This should INSTANTLY destroy the cannon, and initiate the final phase of the fight, where Nitrogg Thundertower reappears and needs to be DPSed down. No further adds will spawn at this point, although all existing adds will remain.

A Hunter can used glyphed Deterrence to the same effect, but a single hunter may not reach 9 stacks of Slag Blast on the Assault Cannon, even with 2 charges of deterrence. Two hunters would definitely be effective in doing so. Even if not quite hitting 9 stacks, a hunter performing this trick will still shorten the length of the fight (likely requiring only 2 Homing Shells to break Nitrogg out, rather than 3-4 normally).

It is essential to be quick about moving out of the fire after 9 stacks are reached, as the Slag Blast will stack on party members quickly once has expired.

Listed at the end of this post is a WeakAura that can be used to track the stacks of Slag Blast, with an alert once 9 stacks are reached.

NOTE: In theory Mass Spell Reflection from a Warrior should work the same way as , but this hasn't been tested, and it is unknown how many stacks of Slag Blast you can reach with this ability.

TL;DR version: Have a DPS attack the cannon at close range. When fire appears around the cannon, drop the Shaman should drop the glyphed , have everyone move into the fire, and have someone shoot the Homing Shell from the Blackrock Turret once there are 9 stacks of Slag Blast on the Assault Cannon. Kill the boss and remaining adds.

A VIDEO GUIDE to the above strategy is available here. Thanks to Jace DK for this great video.

There are a couple of WeakAuras that can be helpful when executing this strategy.

Make sure the "Unit" dropdown shows "Player, and the "Aura Type" is "Buff"

Thanks to Draemii - Tarren Mill EU, Nexxer - Nordrassil EU, Gothunter - Stormrage US, and Babyjace - Kil'jaeden US for some of the information in this post, including the Slag Blast WeakAura above, which is slightly modified from its original form.